I recently decided to stop “running naked.” For the first time as a California homeowner, last month I bought earthquake insurance.

My insurance company offered me a policy for $129 a year. Earthquake coverage suddenly changed from a rip-off, in my admittedly tightwad view of the world, to the deal of the century.

Unfortunately, my happy experience isn’t available to everybody. And this wrinkle in the insurance market shifts massive risks onto California property owners — along with the global financial system that holds their mortgages.

If you think the foreclosure crisis of the last five years was bad, imagine tens of thousands of borrowers walking away from $200 billion in damage that would accompany a 7.8 magnitude earthquake on the San Andreas Fault, according to a 2008 estimate from the U.S. Geological Survey.

Forecasters say there’s a 46 percent chance that a 7.5 quake will hit, probably in Southern California, in the next 30 years, a blink of the eye in geologic time.

The odds of one hitting my house (and maybe yours) are dramatically lower, which is why I got such a great deal on insurance, but I’ll get back to that in a bit.

Merely 12 percent of homeowners in the state buy earthquake coverage, down from 33 percent in the early 1990s.

This means that 88 percent have decided to be self-insured, a position usually taken by corporations or wealthy people who can just write a check to cover losses.

High cost is the main reason — an earthquake policy can cost nearly as much as a home’s basic policy, which covers fire and other losses but not earthquake.

But another big reason for self-insurance is that nobody is making us buy the coverage.

Nearly all mortgage companies require a standard homeowners policy to secure their loans. If they don’t, they can’t sell their mortgages or obtain guarantees from Fannie Mae or Freddie Mac, the federal entities that underwrite most of the nation’s mortgages.

But Fannie and Freddie don’t require earthquake coverage, even though they do require flood insurance in some parts of the country.

Most of the nation’s earthquake risk is concentrated in California, where costs soared after the 1994 Northridge earthquake, which killed 57 people and caused $19 billion in insured losses.

This rattled the insurance industry, because the 6.7 magnitude quake erupted from a previously unknown fault and wiped out the previous 23 years worth of revenues. Insurers had no way to calculate risk, let alone forecast their losses.

In the resulting crisis, the state allowed insurers to divorce earthquake from standard policies and formed the California Earthquake Authority, a state-run, privately funded insurance pool that controls about three-quarters of the market.

Coverage costs have drifted lower since the CEA’s 1996 founding. Last year it cut overall rates by 12.5 percent and expanded its coverage options.

Several factors are driving falling prices. It’s been nearly 20 years since Northridge, so the CEA has been piling up capital without paying out a huge loss.

This has allowed the agency to gradually reduce its costs for reinsurance, the backstop coverage that spreads risk around the globe. Reinsurance gobbles up 40 percent of premiums flowing into the CEA.

Also important is new science that forecast lower risks of losses in many California communities.

Nobody at the CEA or elsewhere could give me details, but this revamping of computer risk models appears to have enabled big price cuts in much of San Diego County.

The authority also now offers more coverage options. You can lower the deductible, raise coverage for household contents, and boost the allowance for living expenses.

Still, earthquake coverage is self-evidently too pricey for most of the state’s homeowners.

And the deductibles remain sky-high, either 10 percent or 15 percent of the estimated cost to rebuild the home, which is the “dwelling value” on the standard homeowners policy.

Such high deductibles have confused consumers and deterred many from buying coverage even as costs have fallen, says Nancy Kincaid, spokeswoman for the California Department of Insurance.

But unlike an auto or health insurance deductible, a property owner isn’t required to actually pay anything if an earthquake destroys the home. Instead, the insurer subtracts the deductible from the cost of reconstruction or repairs.

In the remarkably likely event that my 1969 house is totaled by the Big One, or even a Medium One, I’ll get $228,000 in cool cash to rebuild.

If the worst happens, I will just rebuild a smaller home. The trade-off is that earthquake insurance shoves the risk of relatively minor damage entirely onto me.

This matches up nicely with my approach to risk: I keep high deductibles, and thus low premiums, on all my insurance, including health, auto and homeowners.

For the majority who’d rather remain self-insured, there’s a risk assessment map online at myplan.calema.ca.gov . A brochure at www.earthquakecountry.info has tips on preparing for an earthquake and doing seismic upgrades to your house.

A traditional rule of thumb holds that a family should risk no more than 10 percent of its liquid assets. If the equity in your home surpasses this figure, it’s a good idea to run the numbers to gauge your ability to withstand a total loss of the structure, along with living expenses during reconstruction.

For the cost of $129, which is roughly 10 percent of my annual tab at Starbucks, I’ve stopped throwing earthquake insurance letters into the recycle bin.